1. Field of the Invention
This invention relates to delivery of phenol-modified vegetable oils useful as UV-protective sunscreen agents, antioxidants, skin care agents, cosmetics and the like in starch-based compositions having a continuous aqueous phase and a dispersed oil phase.
2. Description of the Prior Art
An all natural sunscreen active ingredient has been derived from two natural plant components, ferulic acid and soybean oil (SBO) (Compton et al., U.S. Pat. No. 6,346,236). The “green”, enzymatic transesterification between the ethyl ester of ferulic acid, ethyl ferulate (EF), and soybean oil produces a mixture of feruloylated acylglycerols (FAG) that comprise at least monoacyl- and diacyl glycerols that are the major constituents of an all natural, soy-based sunscreen (Laszlo et al., Green Chem. 2003, 5, 382-386). Ferulic acid is a phenolic compound (a member of the cinnamic acid family) that is found esterified in most higher plants with hemicelluloses, lignins, and phytosterols. Thus, ferulic acid is a common component of the human diet. The feruloyl moiety of the FAG has a strong ultraviolet A (UVA) and B (UVB) absorbance while the acylglycerol portion of the FAG provides water resistance (Compton et al., U.S. Pat. No. 6,346,236). These characteristics make FAG a suitable, all natural replacement for commercially used petroleum-based sunscreen active ingredients.
An obvious use of FAG is as a broad UV-absorbing active ingredient in sunscreens, health and beauty aids, and daily wear cosmetics. Formulation and commercialization of FAG into such products is currently being investigated. However, less obvious but important applications also include using FAG as an adjuvant to provide natural UV protection in paints, coatings, and insecticidal and herbicidal biocontrol agents. As most insecticidal and herbicidal agents are aqueous based, it is necessary to formulate water-based systems containing FAG that allow sprayable, uniform films to be prepared. Initial trials to emulsify FAG into aqueous-based agricultural spray formulations using conventional surfactants have met with limited success. The resultant films are non-uniform and do not provide the even coverage needed in agricultural adjuvant applications. An improved, more reliable method for incorporating FAG into aqueous-based agricultural sprays is needed.
An interesting class of highly stable water dispersible starch-lipid composites has recently been developed at our facilities by co-jet cooking starch with lipophilic materials such as vegetable oils under excess steam conditions (Eskins et al., U.S. Pat. No. 5,676,994; Eskins et al., U.S. Pat. No. 5,882,713; Fanta et al., Carbohydr. Polym., 1999, 39, 25-35). The resulting composites can readily contain up to 50% lipophilic material relative to the starch component and are water dispersible over a wide range of dilution. Previous publications (Fanta et al., Carbohydr. Polym., 1995, 28, 171-175; Fanta et al., Carbohydr. Polym., 1999, 39, 25-35; Eskins et al., Carbohydr. Polym., 1996, 29, 233-239) describe the preparation, properties and microscopic analysis of these composites and show the composites to consist of lipid droplets having typical diameters in the 1-10 μm range coated with a thin film of firmly bound starch at the oil-water interface. The water dispersed oil-starch composites can be drum dried to produce oil microencapsulated in starch flakes that are easily reconstituted in water to again form smooth, stable dispersions. These starch-oil composites provide an ideal method to carry lipophilic components into aqueous systems without the need for additional emulsifiers, stabilizers, or surfactants.